The tomato Solanum lycopersicum (formerly Lycopersicon esculentum) is susceptible to a large number of viral species. Some of the most prominent tomato viruses include Tomato spotted wilt virus (TSWV; genus Tospovirus); Pepino mosaic virus (PepMV; genus Potexvirus), and Tomato yellow leaf curl virus (TYLCV; genus Begomovirus). The damage that these diseases inflict on the plant range from discoloration of leaves and necrotic lesions, to severe crop loss and death of the plant.
The ability to provide resistant plants is of utmost importance to commercial breeders, and for some of the economically most damaging viruses, resistant plant varieties have been produced. However, from time to time, new viruses emerge that may inflict considerable damage on crops.
In 1996 a new tomato virus was reported which had infected tomato plants in the USA and Italy since 1993, and was named Tomato infectious chlorosis virus (TICV; genus Crinivirus; Duffus et al., 1996). Another new tomato virus of the same genus was reported in 1998. This virus was shown to have infected tomato plants in the USA since 1989 and was named Tomato chlorosis virus (ToCV; Wisler et al., 1998). Both these new viruses proved to be spread by a whitefly, the insect being a very effective disease-transmission vector.
It is generally believed that the geographic distribution of known viruses will increase and that new viruses will continue to appear, partly as a result of recombination of different viruses to form new strains or new viruses. The development of resistant cultivars can play an important role in the successful management of these diseases.